Stadiametric ranging system

ABSTRACT

Subject disclosure relates to a novel and improved system for determining the range and aspect of an aircraft or any other vehicle moving in three dimensions in relation to a fixed point. The system includes a fixed isoceles right triangular pattern laid out on the ground or an another suitable reference plane, an energy sensor detector on the aircraft that develops an image of triangular pattern, and determines the coordinates of the apices of the pattern, a computer on the aircraft that performs predetermined mathematical operations on the apex coordinate data from the sensor detector and a readout device on the aircraft that continuously provides range and aspect data that defines the position of the aircraft.

ilite tates at r Alhright [451 Apr. 4, 11972 [54] STADHAMETRKQ RANGINGSYSTEM 2,763,856 9/1956 Lattmann ..343/15 [72] Inventor: John D.Albrlght, Beltsville, Md. Primary EXaminer BenJ-amin A. Bmchelt [73]Assignee: The United States at America as Assistant Examiner-S C,Buczinski represented by the Secretary of the Navy Attorney-R. SClQSClHand A. W. COllll'lS [22] Filed: M81. 6, 1970 57 ABSTRACT [21] APPL17,272 Subject disclosure relates to a novel and improved system fordetermining the range and aspect of an aircraft or any other 52 us. (:1.ass/141, 356/1, 343/1 12 R, vehicle mving three dimensions in claimfixed P 235/15O 271 The system includes a fixed isoceles righttriangular pattern [5 l] lint. Cl. ..G0lb 11/26 laid out on the groundor an another uitable reference plane 158 Field of Search ..356/1,141;343/112c, 112 D; an energy Sensor detect alrcfafl that devekps235/1502 150272 image of triangular pattern, and determines thecoordinates of the apices of the pattern, a computer on the aircraftthat per- 56] References Cited forms predetermined mathematicaloperations on the apex coordinate data from the sensor detector and areadout device UNITED STATES PATENTS on the aircraft that continuouslyprovides range and aspect data that defines the position of theaircraft. 2,681,764 6/1954 Gale ..235/150.272 3,244,810 4/1966 Williams..178/DlG. 21 2 Claims, 3 Drawing Figures READOUT DISPLA COMPUTER RV.VIDICON TUBE SENSOR AXIS PATENTEIJAPR 4 I972 3, 658 769 p l 7 5 j 3 IDISPLAY- T.V.V|DICON| I READOUT COMPUTER TUBE SENSOR AXIS Fig. 2

INVENTOR.

JOHN D ALBRIGHT mum,

ATTORNEY STADKAMETRIC HANGING SYSTEM When an aircraft makes an approachto a point on the ground or another reference surface either for anattack or a landing, information in some form which tells the pilotprecisely where he is with respect to the point is often necessary.Large airports often provide extensive runaway lighting systems andvarious intricate non-visual electronic devices to assist landing andother operations at night and at other times where visibility isrestricted. Situations, however, also occur when it is desirable to makea precise approach at an airport where extensive landing aids are notavailable or economically feasible.

It is therefore a principal object of the invention to provide a noveland improved system which continuously and accurately defines theposition of an aircraft or other moving vehicle with respect to a fixedpoint.

It is a further object of the invention to provide a novel and improvedsystem which accurately defines the position of an aircraft withapparatus and circuitry which are relatively simple compared topresently used electronic and radar type devices.

It is a further object of the invention to provide a novel and improvedsystem that accurately defines the position of an aircraft during alanding operation on an aircraft carrier.

It is a further object of the invention to provide a novel and improvedsystem that assists the pilot of an aircraft to set a precise offsetcourse with respect to a known fixed reference point.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing wherein:

FIG. l is a plan view of a preferred triangular pattern of energyprojecting devices laid out on the ground or other reference surface inaccordance with the present invention;

FIG. 2 is a diagrammatic view of the apparatus of the present inventionpositioned on the aircraft and its relation to the fixed triangularpattern on the reference surface;

FIG. 3 is a perspective view of the geometric relations of the aircraftand the triangular pattern on the reference surface.

Referring now to the various figures of the drawing, it will be notedthat three light energy sources A, B and C are laid out on the ground inthe pattern of an isosceles right triangle. The legs AB and BC of thetriangular pattern are of any suitable equal length and the right angleof the triangle is located at the source B. The projected view of thetriangular pattern of the three light sources appears from the aircraftP as in FIG. 2 of the drawing. The aircraft P carries the energy sensordetector 3, which is mounted in any suitable conventional mannerpreferably on an axis parallel to the longitudinal axis of the aircraft,the computer 5 which is coupled to the output of the sensor detector 3,and the display readout device 7 which is coupled to the output of thecomputer.

The structural details of the sensor detector 3, the computer 5 and thereadout device 7 may take any of a number of specific conventionalmechanical and/or electrical forms. Since the details of theirconstruction form no part of the invention, the same are not includedherein for the sake of simplicity. For a full understanding of theinvention, it need only be understood that the energy sensor detector 3preferably includes a telescope 3a and a television vidicon tube 3bhaving a sensing area of approximately inch square. The telescopevidicontube assembly is gimbal mounted in a protective housing on the aircraftpreferably under the fuselage of the aircraft or in a pod under a wing.The computer 5 is preferably a digital logic package of integrated solidstate circuitry such as a UNIVAC l 108. It must be fast enough tocompute new output parameters for each frame of the vidicon TV raster.Using various general geometric relations of the triangular pattern ofthe three light energy sources A, B and C on the ground as it isprojected up to the aircraft P, the computer 5 is programmed to acceptdata read from the projected pattern by the sensor detector 3 anddetermine the range from the aircraft to K tan B 01=8FC sin (I) l K tan/3 and that sin a [m+smatanfl:l (2) 0 arc tan COS" (r where a is thedown look angle of the telescope on the aircraft to the point B, K isthe ratio L /L, (L and L being the projected lengths of triangle legs ABand BC to the down look sight line PB), B is the azimuth angle on theground between the sight line projection and the foreshortened leg BC ofthe triangle, and 0 is an angle between the extremities of the projectedlegs of the triangular pattern.

The coordinates of points A, B and C which are continuously furnished tothe computer 5 by the sensor-detector 3 are used to determine 6 and 0,the projected lengths L and L and the ratio K directly. Equations (1)and (2) therefore involve two known quantities 6 and K) and two unknowns(a and B). A simultaneous solution of equations (1) and (2) in thecomputer 5 produces the values of a and ,8.

It can also be shown that the range of the aircraft P to ground point Balong the down look sight axis PB in FIG. 3 of the drawing is given bythe equation:

3) tantb where is range PB to ground point B, L is the true lengthoftriangle legs AB and BC, and 0 is the angle subtended by theprojection of the foreshortened leg BC of the triangle.

It can also be shown that:

h R sin a where h is the altitude of the aircraft above the ground.

Thus, it is seen that knowing the true dimensions of the ground lightpattern and the coordinates of each of the light sources A, B and C, thecomputer 5 can be programmed in a suitable conventional manner toprovide the range, altitude, azimuth and other positional data of theaircraft at all times.

In operation, when the telescope of the sensor detector 3 is directedtoward the preset triangular pattern of light energy sources A, B and Con the ground, the telescope projects an image in the visible lightfrequency range on the vidicon tube surface. The tube surface is thenscanned in a TV type raster operation and the positions of the lightsources of the pattern on the light sensitive surface are detected. Thevideo output pulses of the vidicon on the raster then determine thecoordinates of the projected pattern points A, B and C with respect tothe optical axis of the telescope-vidicon tube assembly. The coordinatepulses of points A, B and C are then fed to the computer 5 whichperforms the computations indicated and outlined in detail hereinabove.The readout device 7 coupled to the output of the computer 5continuously displays the range and aspect data with respect to thetriangular pattern on the ground.

It is to be understood that, although the markers which define theapices of the triangular ground pattern are disclosed herein as beingactive light energy sources, any other suitable active energy radiatoror passive energy reflector could be used without departing from thespirit or scope of the invention.

Similarly, it is to be understood that any triangular or geometricground pattern other than the isosceles right triangular patterndisclosed herein could be used without departing from the spirit orscope of the invention by suitable adjustment of the preset mathematicoperations in the computer.

it is also to be understood that, although the sensor-detector describedherein operates in the visible light frequency region, any suitable partof the electromagnetic spectrum could be used without departing from thespirit or scope of the invention.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is: r

1. Apparatus for determining the position of an aircraft in relation tothe ground, said apparatus comprising:

a. three light energy sources positioned on the ground in an isoscelesright triangular pattern;

b. an energy sensor detector positioned on the aircraft which developsan image of the triangular pattern and determines various parameters ofthe pattern image, said detector including a telescope device mounted onan axis parallel to the longitudinal axis of the aircraft and atelevision vidicon tube;

0. and a computer on the aircraft which is coupled to detector and whichperforms predetermined mathematical operations including the solution ofthe following equations for a and ,8:

lK tan /3 (1) sin a m where a is the down look angle of the telescopedevice on the aircraft to the apex of the right angle of the groundtriangular pattern, K is the ratio L lL (L, and L being the projectedlengths of the legs of the triangular pattern to the extended axis ofthe telescope device), [3 is the azimuth angle on the ground betweenprojection on the ground of the extended axis of the telescope deviceand a foreshortened leg of the triangular pattern, and 0 is the anglebetween the extremities of the projected legs of the triangular pattern.2. The apparatus substantially as described in claim 1 wherein themathematical operations of the computer further include solution of thefollowing equation:

. 1cos acos /3 RL cosacosB+ tam!)

1. Apparatus for determining the position of an aircraft in relation tothe ground, said apparatus comprising: a. three light energy sourcespositioned on the ground in an isosceles right triangular pattern; b. anenergy sensor detector positioned on the aircraft which develops animage of the triangular pattern and determines various parameters of thepattern image, said detector including a telescope device mounted on anaxis parallel to the longitudinal axis of the aircraft and a televisionvidicon tube; c. and a computer on the aircraft which is coupled todetector and which performs predetermined mathematical operationsincluding the solution of the following equations for Alpha and Beta :2. The apparatus substantially as described in claim 1 wherein themathematical operations of the computer further include solution of thefollowing equation: where R is the range of the aircraft to the apex ofthe right angle of the triangular pattern, L is the ground length of thelegs of the triangular pattern, and theta is the angle between theextremities of the projected said foreshortened leg of the triangularpattern.